1. Field of the Invention
The present invention relates generally to methods and systems for removing liquids from surfaces of semiconductor substrates such as wafers. More particularly, the present invention relates to systems and methods for reducing or eliminating the presence of residues on a substrate surface following the removal of liquids therefrom by selective manipulation of the liquids on the substrate surface.
2. Discussion of Related Art
Integrated circuit devices such as microprocessors and memory devices are typically fabricated upon a semiconductor substrate, such as a full or partial wafer of semiconductor material (e.g., silicon, indium phosphide, gallium arsenide, etc.), or other substrate including one or more layers of semiconductor material thereon, such as a silicon-on-insulator (SOI) type substrate (such as, a silicon-on-glass (SOG), silicon-on-sapphire (SOS), silicon-on-ceramic (SOC), etc.), or any other suitable fabrication substrate. A large number of identical integrated circuit devices typically are fabricated on a single substrate, and the substrate is then diced, sawed, or cut, to physically separate individual semiconductor devices from one another.
Semiconductor substrates are subjected to a significant number of individual processes during the fabrication of integrated circuitry thereon. These processes often include growth or deposition of material layers, ion doping or implanting, photolithography processes, etc. These processes may be preceded or followed by cleaning steps that involve, for example, scrubbing, spray cleaning, and other such processes. At the completion of cleaning, the substrate may be further processed to remove the cleaning agents and contaminant materials from the surface of the substrate to prevent the formation of contaminating residue on the substrate surface. Often, the last step in a cleaning process includes a rinsing step using clean, de-ionized water followed by a drying process.
For example, it is known in the art to spin a fabrication substrate about a rotational axis extending through the center of the substrate and perpendicular to a major plane thereof while directing a stream of clean de-ionized water onto a surface of the substrate. A substrate may be placed in a spin rinse drier (SRD) that includes a platform coupled to a drive motor. The drive motor may cause the platform to spin at a velocity of, for example, up to 4,000 revolutions per minute (rpm). A stream of water may be directed onto the surface of the substrate while it is spinning to rinse contaminants from the surface of the substrate.
Typically, a rinse liquid is applied to an entire surface of the substrate, including the center of rotation thereof, which is a point on the surface at which the axis about which the substrate is rotated intersects the surface of the substrate to which liquid is applied and removed. As the substrate spins, centrifugal forces cause the liquid to fan out across the surface of the substrate, thereby forming a substantially continuous sheet or film of liquid covering the surface of the substrate. To dry the surface of the substrate, the substantially continuous sheet or film of liquid is removed from the surface of the substrate by interrupting the flow of liquid onto the surface of the substrate while continuing to spin the substrate. Centrifugal forces acting on the liquid cause it to slide off from (or otherwise be removed from) the surface of the substrate in a generally radially outward direction from the center of rotation towards the lateral edges of the substrate.
Often, traces or residue of contaminant material or other unwanted matter, which may be referred to as “water marks” or “doilies,” are left behind on the surface of the substrate after the liquid has been removed from the substrate. These traces or residue may include solid matter such as, for example, silica or other materials left behind by prior processing of the substrate, and generally are undesirable as they may interfere with subsequent processing of the substrate. For example, if the rinse process is followed by an etch process in which a portion of the substrate underlying a water mark is to be etched, the solid matter forming the water mark may act as a mask to prevent or block the etch process on the underlying surface of the subject, thereby generating a defect in the structure being defined by the etch on the substrate. If the rinse process is followed by an ion implant process, in which ions of a selected material are to be implanted in a portion of the substrate underlying a water mark, the solid matter forming the water mark may prevent or block the ion implant process, thereby generating a defect in the portion of the substrate, such as a source or drain region, being implanted.
In view of the foregoing, it would be desirable to provide methods and systems for rinsing and drying a semiconductor substrate such as a wafer that minimizes water marks or other contaminant residue or matter left behind on the surface of the substrate.